Abstract: The research emphasises the necessity of a deep knowledge of the wall morphology and of the components, of their characteristics and of the eventual state of damage and its causes , when approaching the modelling of an historic stone masonry structure. A classification of historic masonry buildings together with a classification of single and multiple leaf masonry sections according to the number of leaves and their connections as a result of a long term investigation carried out in different Italian Regions will be presented. It will also be shown how without this knowledge incompatible techniques for repair can be adopted which can cause damages under seismic events.